test: improve coverage

Author: MilesCranmer

test/test_composable_expression.jl

@@ -185,7 +185,7 @@ end
 
 @testitem "ValidVector operations with Union{} return type" tags = [:part2] begin
     using SymbolicRegression: ValidVector
-    using SymbolicRegression.ComposableExpressionModule: apply_operator
+    using SymbolicRegression.ComposableExpressionModule: apply_operator, _match_eltype
 
     error_op(::Any, ::Any) = error("This should cause Union{} inference")
 
@@ -201,4 +201,17 @@ end
     b = 1.0
     result2 = apply_operator(*, a, b)
     @test result2 isa ValidVector{<:AbstractArray{Float64}}
+
+    # Test apply_operator when all inputs are valid
+    valid_x = ValidVector([1.0, 2.0], true)
+    valid_y = ValidVector([3.0, 4.0], true)
+    valid_result = apply_operator(+, valid_x, valid_y)
+    @test valid_result.valid == true
+    @test valid_result.x ≈ [4.0, 6.0]
+
+    # cover _match_eltype
+    arr = [1.0, 2.0]
+    @test _match_eltype(ValidVector{Vector{Float64}}, arr) === arr  # Same type
+    arr_f32 = Float32[1.0, 2.0]
+    @test _match_eltype(ValidVector{Vector{Float64}}, arr_f32) isa Vector{Float64}  # Different type
 end

test/test_template_expression.jl

@@ -696,6 +696,7 @@ end
 @testitem "Test Float32/Float64 type conversion in TemplateExpression" tags = [:part2] begin
     using SymbolicRegression
     using SymbolicRegression: eval_loss
+    using SymbolicRegression.TemplateExpressionModule: _match_input_eltype
 
     template = @template_spec(expressions = (f,)) do x1, x2
         0.5 * f(x1, x2)  # 0.5 is Float64 literal
@@ -719,4 +720,10 @@ end
     loss = eval_loss(template_expr, dataset, options)
     @test loss isa Float32
     @test loss ≈ 0.0
+
+    # Test _match_input_eltype coverage (covers lines 675-676)
+    result_f64 = [1.0, 2.0]
+    @test _match_input_eltype(Matrix{Float64}, result_f64) === result_f64  # Same type
+    result_int = [1, 2]
+    @test _match_input_eltype(Matrix{Float64}, result_int) === result_int  # Non-float type
 end